JPH0691281A - Treatment of organic waste water containing phosphorus - Google Patents

Abstract

PURPOSE:To treat a waste water efficiently at a low treatment cost by treating a water treated by wet type oxidation to remove carbonic acid and adding a calcium compound to the resulting waste water, regarding a treatment method which involves calcium compound addition after wet type oxidization treatment of organic waste water containing phosphorus and removal of phosphorus by making the phosphorus insoluble. CONSTITUTION:Raw water containing the substances to be oxidized and phosphorus is supplied to a wet type oxidation reaction tower 1, the substances are oxidized and decomposed, the resulting gas-liquid mixed solution is separated in a gas-liquid separating tower 2, and the gas is released to air and the separated liquid is sent to a carbonic acid removing tower 3. Carbonic acid is efficiently removed in the carbonic acid removing tower 3 and a calcium compound such as slaked lime, etc., is added to the resulting carbonic acid-removed water in a reaction tank 4 where phosphorus is made insoluble, and a part of SS is also returned from a solid-liquid separation tank 5 in a post stage. The slaked lime and carbonic acid-removed water are mixed and stirred in the reaction tank 4 and phosphorus is converted into hydroxyl apatite and thus becomes insoluble. Separation treatment is then carried out in a solid-liquid separation tank 5 and the supernatant water is discharged outside and a part of separated sludge is returned to the reaction tank 4 and the rest is discharged outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating an organic wastewater containing phosphorus, and more particularly, to a high-concentration organic wastewater containing phosphorus such as human waste which is subjected to a wet oxidation treatment and then a calcium compound is added thereto
In a method for insolubilizing and removing phosphorus, the present invention relates to a method for treating organic wastewater containing phosphorus for reducing the amount of calcium compound used and the amount of sludge generated.

[0002]

2. Description of the Related Art Conventionally, wastewater containing a relatively high concentration of oxides such as human waste, sewage or excess sludge generated when biologically treating human waste, digested sludge, coal gasification / liquefaction wastewater, BACKGROUND ART Wet oxidation treatment is performed as a treatment method of wastewater generated by thermal decomposition of municipal waste, factory wastewater discharged from yarn mills, fiber dyeing factories, food factories, chemical factories, petroleum refining factories and other various factories.

In this wet oxidation treatment, the above-mentioned wastewater is introduced into a wet oxidation reaction tower consisting of a high-pressure tank and maintained at high temperature and high pressure in the presence of oxygen so that the oxides to be oxidized are carbon dioxide gas, nitric acid,
It decomposes into nitrogen gas and water, and in this case, in order to efficiently carry out the oxidative decomposition reaction, a filling tank of an oxidation catalyst is built in the wet oxidation reaction tower.

As the oxidation catalyst, titania (titania oxide), zirconia (zirconia oxide), alumina,
Silica, silica-alumina, activated carbon, or nickel,
Nickel-chromium, nickel-chromium-aluminum,
Iron-manganese-cobalt-nickel-ruthenium-rhodium-palladium-iridium-platinum-copper-gold and tungsten and their oxides, and ruthenium dichloride and dichloride A substance in which a compound such as a chloride such as platinum chloride or a sulfide such as ruthenium sulfide or rhodium sulfide and which is insoluble or hardly soluble in water is supported is used.

However, as a method for further removing phosphorus from the wet oxidation treated water from such a wet oxidation reaction tower,
A reaction solution is solid-liquid separated by adding a phosphorus insolubilizer (for example, JP-A-2-31889 and 2-3).
1896).

[0006]

However, in the above conventional treatment method, the phosphorus insolubilizing agent is added to the treated water of the wet oxidation reaction tower to remove the phosphorus, so that the phosphorus insolubilizing agent is removed. However, there is a drawback that the drug cost is high because of the large amount used.

That is, since the treated water from the wet oxidation reaction tower contains a large amount of carbonic acid, which is a decomposition product of the treated water, the treated water is directly treated with a phosphorus insolubilizing agent such as calcium hydroxide (Ca (OH)). ₂ ) is added, this C
a (OH) ₂ is consumed in the reaction with carbonic acid.

Moreover, there is also a drawback that calcium carbonate sludge produced by the reaction between Ca (OH) ₂ and carbonic acid is produced, and the disposal cost thereof is high.

The present invention solves the above-mentioned conventional problems, and in a method of wet-oxidizing a high-concentration organic wastewater containing phosphorus such as human waste and then adding a calcium compound to insolubilize and remove phosphorus, It is an object of the present invention to provide a method for treating organic wastewater containing phosphorus, which can reduce the amount used and the amount of sludge generation.

[0010]

The method for treating organic wastewater containing phosphorus according to the present invention comprises subjecting organic wastewater containing phosphorus to wet oxidation treatment, adding a calcium compound to the treated water, and insolubilizing phosphorus. In the removing method, the wet oxidation treated water is decarbonated, and then a calcium compound is added.

[0011]

In the method for treating organic wastewater containing phosphorus of the present invention, the wet oxidation treated water is decarbonated prior to the addition of the calcium compound, so that the carbonation in the wet oxidation treated water is removed by this decarboxylation treatment.

Therefore, the calcium compound is not consumed by the reaction with carbonic acid in the wet oxidation treated water, and the amount of the calcium compound used can be reduced. In addition, the amount of generated sludge is reduced without generating sludge of calcium carbonate due to the reaction between the carbonic acid in the wet oxidation treated water and the calcium compound.

Therefore, the chemical cost and the sludge disposal cost can be reduced, and the treatment efficiency and the treatment cost can be greatly improved.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of the method for treating organic wastewater containing phosphorus according to the present invention.

In the figure, reference numeral 1 is a wet oxidation reaction column comprising a high-pressure tank filled with a known oxidation catalyst 1A. The wet oxidation reaction tower 1 is heated to 250 by a heating means (not shown).
It is heated to ~ 290 ° C and is heated to 70
The pressure is increased to 90 kg / cm ² , and oxygen is further supplied by the gas supply means.

Although the heating is performed by an external heat source at the time of starting the apparatus, it can be performed by oxidative combustion in raw water when the apparatus is in a steady operation state.

Although the wet oxidation reaction tower 1 does not necessarily need to be filled with an oxidation catalyst, it can be efficiently oxidized by filling it with the oxidation catalyst 1A as in this embodiment.

The wet oxidation reaction tower 1 has a raw water supply pipe 11
Raw water containing oxidant and phosphorus is supplied from the oxidant, the oxidant in the raw water is oxidized in the wet oxidation reaction tower 1 and decomposed into carbon dioxide gas, nitrogen gas, and water, and the gas-liquid mixed liquid is pipe 1
It is fed to the gas-liquid separation tower 2 via 2. The pipe 12 is provided with a heat exchanger (not shown), by which the raw water in the raw water supply pipe 11 is heat-exchanged and heated to recover heat.

The gas component separated in the gas-liquid separation column 2 is sent to the cyclone separator through a pipe 13 equipped with a pressure reducing valve (not shown), and the gas separated by the cyclone separator is released to the atmosphere. On the other hand, the separated liquid of the gas-liquid separation tower 2 is fed to the decarbonation tower 3 described later through the pipe 14. The separated liquid component of the cyclone separator is also sent to the decarbonation tower 3 together with this separated liquid.

The type of the decarbonation tower 3 is not particularly limited, and may be filled with Raschig rings 3A and the like, and a method of blowing air or N ₂ gas from the lower part of the tower through the pipe 15 or aeration from the lower part of the water bottom. The operating pressure may be either normal pressure or reduced pressure.

In the decarbonation tower 3, carbon dioxide in the wet oxidation treated water is efficiently removed, and the decarbonated water from which the carbonic acid is removed is supplied to the phosphorus insolubilization reaction tank 4 through the pipe 16.

In the phosphorus insolubilization reaction tank 4, a calcium compound such as slaked lime (Ca (OH) ₂ ) is added as an insolubilizing agent from a pipe 17, and a part of SS from the solid-liquid separation tank 5 in the subsequent step is added. Returned from the pipe 18. here,
The amount of Ca (OH) ₂ added is controlled by the pH meter 4A,
Normally, C is adjusted so that the pH is about 9.5 to 10.5.
Addition of a (OH) ₂ is performed. 4B is a stirrer.

As the calcium compound of the phosphorus insolubilizing agent, quick lime, calcium chloride, etc. may be used in addition to Ca (OH) ₂ .

When Ca (OH) ₂ and decarbonated water are mixed and stirred in the phosphorus insolubilization reaction tank 4, phosphorus in the decarbonated water is converted into hydroxylapatite (Ca ₅ OH (PO ₄ )).
₃ ) and becomes insoluble. The treated water containing insolubilized phosphorus is fed to the solid-liquid separation tank 5 through the pipe 19 for separation treatment. Here, in order to clarify the treated water, the polymer coagulant is directly or directly supplied to the pipe 19. It is advisable to install a separate reaction tank and add the solution.

The supernatant water of the solid-liquid separation tank 5 is discharged to the outside of the system through the pipe 20 as treated water, while a part of the separated sludge is returned to the phosphorus insolubilization reaction tank 4 through the pipe 18 and the rest is left. Is discharged from the system through the pipe 21.

As the solid-liquid separation tank 5, a precipitation tank, a sand filtration tank, a membrane filtration device or the like can be applied.

The present invention will be described in more detail below with reference to specific examples and comparative examples.

Example 1 By the method of the present invention shown in FIG. 1, human waste was treated under the following treatment conditions at a flow rate of 850 liters / hr, and the amount of Ca (OH) ₂ added to the phosphorus insolubilization reaction tank and the treatment were performed. Table 1 shows the phosphorus concentration of water and the amount of sludge generated.

Treatment condition Wet oxidation reaction tower: Temperature = 270 ° C. Pressure = 90 kg / cm ² Residence time = 90 minutes Decarbonation tower: Residence time = 16 minutes Air amount (G / L) = 10 Phosphorus insolubilization reaction tank: pH = 10.0 Amount of sludge returned = 50% with respect to the amount of raw water Comparative Example 1 The amount of Ca (OH) ₂ added to the phosphorus insolubilization reaction tank which was treated in the same manner as in Example 1 except that no decarbonation tower was provided. Table 1 shows the phosphorus concentration and the amount of sludge generated in the treated water.

[0031]

[Table 1]

As is clear from Table 1, by performing the decarboxylation treatment prior to the phosphorus insolubilization treatment according to the method of the present invention, the required addition amount of the calcium compound and the sludge generation amount can be greatly reduced.

[0033]

As described above in detail, according to the method for treating organic wastewater containing phosphorus of the present invention, the organic wastewater containing phosphorus is subjected to wet oxidation treatment, the calcium compound is added to the treated water, and phosphorus is added. In the method of insolubilizing and removing slag, the amount of calcium compound used is reduced and the amount of sludge generated is significantly reduced, and the chemical cost and sludge treatment cost are reduced. Therefore, it becomes possible to efficiently treat the organic wastewater containing phosphorus at a low treatment cost.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a method for treating organic wastewater containing phosphorus according to the present invention.

[Explanation of symbols]

 1 Wet oxidation reaction tower 2 Gas-liquid separation tower 3 Decarbonation tower 4 Phosphorus insolubilization reaction tank 5 Solid-liquid separation tank

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kenichi Yamazaki 4-1-2, Hirano-cho, Chuo-ku, Osaka City, Osaka Prefecture Osaka Gas Co., Ltd. (72) Noboru Yamada 3--4, Nishi-Shinjuku, Shinjuku-ku, Tokyo No. 7 In Kurita Industry Co., Ltd. (72) Inventor Tadashi Takadoi 3-4 Nishi-Shinjuku, Shinjuku-ku, Tokyo No. 7 In Kurita Industry Co., Ltd. (72) Yoshihiro Eto 3-4 Nishi-Shinjuku, Shinjuku-ku, Tokyo No. 7 Kurita Industry Co., Ltd.

Claims (1)

[Claims] 1. A method of subjecting an organic wastewater containing phosphorus to a wet oxidation treatment, adding a calcium compound to the treated water to insolubilize and remove phosphorus, wherein the wet oxidation treated water is decarboxylated, and then calcium is added. A method for treating organic wastewater containing phosphorus, which comprises adding a compound.